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Instream player, outstream player, vpaid: plcmt, video.placement and other video values are automatically set in prebid, prebid server and rtb demand. Add [AVC_PLCMT] macro on the vast tags you have in order to pass to vast tags
vast tag (client or servers side): plcmt will pass automatically prebid server and rtb demand
In vast demand tags, use [AV_PLCMT] that will be replaced with AV_PLCMT used in the vast call from supply
Other video parameters must be defined in the prebid server/rtb ad source page
prebid tags do not work in vast anyway